Digital Modulator and Method for Initiating Ramp Power Transitions in a Mobile Handset Transmitter

ABSTRACT

A digital modulator for a portable handset using 8PSK or EDGE modulation with a direct launch transmitter is used to controllably adjust the transmit power of the portable handset. The digital modulator includes a controller coupled between a memory and an accumulator. The controller is responsive to an indication that the transmit power should be transitioned. The controller temporarily alters the data transferred from the memory to the accumulator during transitions of the transmit power level.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to copending U.S. provisionalapplication titled “IQ Ramp Down for 8PSK Modulation in EDGE Phone,”having Ser. No. 60/896,025 filed on Mar. 21, 2007, which is entirelyincorporated herein by reference.

BACKGROUND

This invention relates generally to transceiver architecture in awireless portable communication device.

Radio frequency (RF) transmitters are found in many one-way and two-waycommunication devices, such as portable communication devices, (cellulartelephones), personal digital assistants (PDAs) and other communicationdevices. An RF transmitter must transmit using whatever communicationmethodology is dictated by the particular communication system withinwhich it is operating. For example, communication methodologiestypically include amplitude modulation, frequency modulation, phasemodulation, or a combination of these. In a typical global system formobile communications (GSM) mobile communication system using narrowbandtime-division multiple access (TDMA), a Gaussian minimum shift keying(GMSK) modulation scheme is used to communicate data.

The deployment of new wireless systems presents unique challenges tomobile handset designers. In order to reap the full benefit of expandedcapacity and increased data bandwidth, the new handsets must work onboth the new systems as well as the old.

One of these new systems has been named Enhanced Data Rates for GSMEvolution (EDGE). The EDGE standard is an extension of the Global Systemfor Mobile Communications (GSM) standard.

The EDGE standard increases the data rate over that available with GSMby sending more bits per RF burst. More bits are sent in EDGE by using amodulation scheme based on 8-phase shift keying (8PSK), which providesan increase over GSM's Gaussian minimum shift keying (GMSK) modulationformat. In the EDGE modulation scheme, the 8PSK constellation is rotated⅜ radians every symbol period to avoid problems associated with zerocrossings. In contrast to GMSK's constant amplitude envelope, the EDGEmodulation scheme results in a non-constant amplitude envelope.

This non-constant amplitude in the output signal presents somedifficulties with regard to RF power control.

During multi-slot operation of a mobile handset transmitter using 8PSKmodulation, the power of the modulated radio-frequency (RF) signal isrequired to ramp-up to a desired power level for a set period of timeduring which the handset transmits encoded data symbols. After thetransmission has completed, the power of the modulated RF signal isrequired to return or ramp down to an off power level. The ramp-up andramp-down must be accomplished without adversely affecting time andfrequency parameters defined by the EDGE communication standard.

One conventional approach to power control generates a signal that isused to controllably adjust the gain of a variable gain amplifierlocated in series with a linear power amplifier. For polar looptransmitter architectures, which are already operating near saturationin 8PSK mode, power control has been accomplished through poweramplifier bias controls. These conventional power controllers requireintegrated circuit space, increase the power budget of the mobilehandset and for some conditions require a longer time than thatavailable to meet frequency spectrum requirements.

Another approach is introduced in U.S. Patent Application Publication2005/0249312 to Bode et al. (the '312 publication). The '312 publicationdescribes a digital modulator that introduces dips in the envelope ofthe I/Q signal between adjacent time intervals or bursts. A dip-shapedwaveform is multiplied with each of the I and Q waveforms to introducethe dips. A pulse-shaping filter is used with the dip-shaped waveform toobtain the desired result in the envelope of the I/Q signal. Thissolution requires additional memory to store the dip waveform andintegrated circuit space to implement the pulse-shaping filter.

Therefore, it would be desirable to provide dynamic power control in amobile handset in an economic and efficient manner and in accordancewith the EDGE communication standard across a broader range of operatingconditions absent additional memory capacity or shaping filters.

SUMMARY

An embodiment of a digital modulator and method for initiating ramppower transitions in a mobile handset includes a memory, an accumulatorand a controller inserted between the memory and the accumulator. Thecontroller alters the transfer of stored symbols to the accumulator inresponse to an indication that the transmit power should betransitioned.

An embodiment of method for initiating ramp power transitions in amobile handset includes the steps of inserting a controller between amemory element and an accumulator in a modulator and controllablydirecting the controller to alter the transfer of stored symbols fromthe memory element to the accumulator by applying a logic 0 at an inputof the accumulator in response to an indication that the transmit powershould be transitioned.

The figures and detailed description that follow are not exhaustive. Thedisclosed embodiments are illustrated and described to enable one ofordinary skill to make and use the digital modulator and method forinitiating ramp power transitions in a mobile handset. Otherembodiments, features and advantages of the modulator and method will beor will become apparent to those skilled in the art upon examination ofthe following figures and detailed description. All such additionalembodiments, features and advantages are within the scope of thedisclosed systems and methods as defined in the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

The digital modulator and method for initiating ramp power transitionsin a mobile handset can be better understood with reference to thefollowing figures. The components within the figures are not necessarilyto scale, emphasis instead being placed upon clearly illustrating theprinciples and operation of the modulator and the method. Moreover, inthe figures, like reference numerals designate corresponding partsthroughout the different views.

FIG. 1 is a block diagram illustrating a simplified portable transceiverincluding a direct launch transmitter.

FIG. 2 is a schematic diagram illustrating an example embodiment of thedirect launch transmitter of FIG. 1.

FIG. 3 is a schematic diagram of an embodiment of the digital modulatorof FIG. 2.

FIGS. 4A and 4B are graphical representations of the modulated signalpower vs. time generated by the digital modulator and I/Q controller ofFIG. 3.

FIG. 5 is a flow chart illustrating an embodiment of a method forinitiating power transitions in a mobile handset.

FIG. 6 is a flow chart illustrating an embodiment of an alternativemethod for initiating power transitions in a mobile handset.

DETAILED DESCRIPTION

Although described with particular reference to a portable transceiveroperating under the EDGE (8PSK) modulation scheme, the modulator,controller and method for initiating ramp power transitions in a mobilehandset can be implemented in any communication device where dynamicpower control of a direct launch transmitter is desired.

The modulator, controller and method for initiating ramp powertransitions in a mobile handset can be implemented in hardware,software, or a combination of hardware and software. When implemented inhardware, the modulator, controller and method can be implemented usingspecialized hardware elements and logic. When the modulator, controllerand method are implemented partially in software, the software portioncan be used to control one or more logic components inserted between amemory element and an accumulator so that various operating aspects canbe software-controlled.

The software can be stored in a memory and executed by a suitableinstruction execution system (microprocessor). The hardwareimplementation of the modulator, controller and method for initiatingramp power transitions in a mobile handset can include any or acombination of the following technologies, which are all well known inthe art: discrete electronic components, a discrete logic circuit(s)having logic gates for implementing logic functions upon data signals,an application specific integrated circuit having appropriate logicgates, a programmable gate array(s) (PGA), a field programmable gatearray (FPGA), etc.

The software for the controller and method for initiating ramp powertransitions in a mobile handset comprises an ordered listing ofexecutable instructions for implementing logical functions, and can beembodied in any computer-readable medium for use by or in connectionwith an instruction execution system, apparatus, or device, such as acomputer-based system, processor-containing system, or other system thatcan fetch the instructions from the instruction execution system,apparatus, or device and execute the instructions.

In the context of this document, a “computer-readable medium” can be anymeans that can contain, store, communicate, propagate, or transport theprogram for use by or in connection with the instruction executionsystem, apparatus, or device. The computer readable medium can be, forexample but not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, device,or propagation medium. More specific examples (a non-exhaustive list) ofthe computer-readable medium would include the following: an electricalconnection (electronic) having one or more wires, a portable computerdiskette (magnetic), a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flash memory)(magnetic), an optical fiber (optical), and a portable compact discread-only memory (CDROM) (optical). Note that the computer-readablemedium could even be paper or another suitable medium upon which theprogram is printed, as the program can be electronically captured, viafor instance optical scanning of the paper or other medium, thencompiled, interpreted or otherwise processed in a suitable manner ifnecessary, and then stored in a computer memory.

FIG. 1 is a block diagram illustrating a simplified portable transceiver100 including an embodiment of a direct launch transmitter 200, whichincludes an I/Q generator 136, an I/Q controller 152 for initiating ramppower transitions and a RF upconverter 150 for generating a RF transmitsignal in the portable transceiver 100. The portable transceiver 100includes an input/output (I/O) element 102 coupled to a basebandsubsystem 110 via connection 104. The I/O element 102 represents anyinterface with which a user may interact with the portable communicationdevice 100. For example, the I/O element 102 may include a speaker, adisplay, a keyboard, a microphone, a trackball, a thumbwheel, or anyother user-interface element. A power source 142, which may be a directcurrent (DC) battery or other power source, is also connected to thebaseband subsystem 110 via connection 144 to provide power to theportable transceiver 100. In a particular embodiment, portabletransceiver 100 can be, for example but not limited to, a portabletelecommunication device such as a mobile cellular-type telephone.

The baseband subsystem 110 includes microprocessor (μP) 120, memory 122,analog circuitry 124, and digital signal processor (DSP) 126 incommunication via bus 128. Bus 128, although shown as a single bus, maybe implemented using multiple busses connected as necessary among thesubsystems within baseband subsystem 110.

Depending on the manner in which the I/Q controller 152 and method forinitiating ramp power transitions is implemented, the baseband subsystem110 may also include one or more of an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA), or any otherimplementation-specific or general processor.

Microprocessor 120 and memory 122 provide the signal timing, processingand storage functions for portable transceiver 100. Analog circuitry 124provides the analog processing functions for the signals within basebandsubsystem 110. The baseband subsystem 110 provides data and controlsignals to a radio frequency (RF) subsystem 130. The RF subsystem 130receives data from remote transmitters and forwards the received data tothe baseband system 110 for further processing. The RF subsystem 130includes the direct launch transmitter 200, a receiver 170, a poweramplifier 160, and a power amplifier controller 190. The elements withinthe RF subsystem 130 can be controlled by signals from the basebandsubsystem 110 via bus 132, which is connected to various basebandelements via bus 128. Alternatively, the direct launch transmitter 200and the receiver 170 may be located on an RF integrated circuit (IC).

The baseband subsystem 110 generates various control signals, such as apower control signal, that are used to control the power amplifiercontroller 190 and the power amplifier 160, as known to those skilled inthe art. The control signals on connection 132 may originate from theDSP 126, the microprocessor 120, or from any other processor within thebaseband subsystem 110, and are supplied to a variety of connectionswithin the direct launch transmitter 200, receiver 170, power amplifier160, and the power amplifier controller 190. It should be noted that,for simplicity, only the basic components of the portable transceiver100 are illustrated herein. The control signals provided by the basebandsubsystem 110 control the various components within the portabletransceiver 100. Further, the functions within the direct launchtransmitter 200 and the receiver 170 may be integrated into atransceiver.

The power amplifier controller 190 generates a power amplifier (PA)power control signal. The power control signal is coupled to the poweramplifier 160 via connection 195. The power control signal controls thepower output of the power amplifier 160 based on various inputs. Forexample, in an embodiment, a closed power control loop may influence thepower output of the power amplifier 160. In another embodiment, an openpower control loop may influence the power output of the power amplifier160. For example, in an embodiment, a signal received by a base stationwith which the portable communication device 100 is communicating mayissue a power control signal. In other embodiments, the basebandsubsystem 110 provides enable, standby and power control signals to thepower amplifier controller 190. In turn, the power amplifier controller190 processes the enable, standby and power control signals andgenerates a power control signal that is communicated to the poweramplifier 160 on connection 195.

If portions of the I/Q controller 152 and method for initiating ramppower transitions in a mobile handset are implemented in software thatis executed by the microprocessor 120, the memory 122 will also includeI/Q controller software 156. The I/Q controller software 156 comprisesone or more executable code segments that can be stored in the memory122 and executed in the microprocessor 120. Alternatively, thefunctionality of the I/Q controller software 156 can be coded into anASIC (not shown) or can be executed by an FPGA (not shown), or anotherdevice or may be integrated into a transceiver. Because the memory 122can be rewritable and because a FPGA is reprogrammable, updates to theI/Q controller software 156 can be remotely sent to and saved in theportable transceiver 100 when implemented using either of thesemethodologies.

RF subsystem 130 also includes analog-to-digital converter (ADC) 134 andan in-phase quadrature-phase (I/Q) generator 136. In this example, theI/Q generator 136 generates the in-phase (I) and quadrature-phase (Q)signals that are 8PSK modulated signal before being forwarded to the RFupconverter 150 via connection 140. The ADC 134 and the I/Q generator136 also communicate with microprocessor 120, memory 122, analogcircuitry 124 and DSP 126 via bus 128. The I/Q generator 136 convertsthe digital communication information within baseband subsystem 110 intoa digital signal for further processing by the RF upconverter 150 fortransmission by the direct launch transmitter 200.

The I/Q generator 136 includes an 8PSK modulator that will be explainedin greater detail in association with FIG. 3. The I/Q generator 136 and8PSK modulator operate in accordance with a control signal provided onconnection 153 from the I/Q controller 152. The I/Q controller 152,operating in accordance with one or more signals on bus 132,controllably interrupts the transfer of a modulated I signal and amodulated Q signal to respective transmit chains and mixers forupconversion to a transmit frequency. The RF upconverter 150 of thedirect launch transmitter 200 combines and transforms the modulatedsignals to an appropriate transmit frequency and provides theupconverted signal to the power amplifier 160 via connection 155. Thepower amplifier 160 amplifies the signal to an appropriate power levelfor the system given present conditions under which the portabletransceiver 100 is operating.

The I and Q components may take different forms and be formatteddifferently depending upon the communication standard being employed.For example, when the power amplifier 160 is used in aconstant-amplitude, phase (or frequency) modulation application such asthe global system for mobile communications (GSM), the phase modulatedinformation is provided by a modulator within the direct launchtransmitter 200. When the power amplifier 160 is used in an applicationrequiring both phase and amplitude modulation such as, for example,extended data rates for GSM evolution, referred to as EDGE, theCartesian in-phase (I) and quadrature (Q) components contain bothamplitude and phase information.

The power amplifier 160 supplies the amplified signal via connection 161to a front end module 162. The front end module 162 comprises an antennasystem interface that may include, for example, a diplexer having afilter pair that allows simultaneous passage of both transmit signalsand receive signals, as known to those having ordinary skill in the art.The transmit signal is supplied from the front end module 162 to theantenna 165.

A signal received by an antenna 165 is directed from the front endmodule 162 to the receiver 170. The receiver 170 includes variouscomponents to downconvert, filter, demodulate and recover a data signalfrom a received signal, as known to those skilled in the art. Ifimplemented using a direct conversion receiver (DCR), the receiver 170converts the received signal from an RF level to a baseband level (DC),or a near-baseband level (˜100 kHz). Alternatively, the received RFsignal may be downconverted to an intermediate frequency (IF) signal,depending on the system architecture. The recovered transmittedinformation is supplied via connection 180 to the ADC 134. The ADC 134converts these analog signals to a digital signal at baseband frequencyand transfers the signal via bus 128 to DSP 126 for further processing.

FIG. 2 is a schematic diagram illustrating details of an exampleembodiment of the direct launch transmitter 200 along with the variablegain amplifier 250, the power amplifier 160, front end module 162 andantenna 165 of FIG. 1. The direct launch transmitter 200 includes theI/Q controller 152, the I/Q generator 136 with an integrated 8PSKmodulator 300, the RF upconverter 150 and a frequency generator 260. TheRF upconverter 150 includes a digital-to-analog converter (DAC) 202, DAC204, low-pass filter (LPF) 206, LPF 208, mixer 220, mixer 230, 90° phaseshifter 210 and node 240.

The frequency generator 260 includes a fractional phase-locked loop(PLL) element 265, a voltage-controlled oscillator (VCO) 270, a LPF 275,and a LO processor 280 in a frequency processing portion.

The frequency generator 260 of the direct launch transmitter 200receives a channel reference frequency on connection 252. The channelreference frequency may originate in a reference oscillator located inthe baseband subsystem 110 or in the RF subsystem 130 of the portabletransceiver 100. The channel reference frequency is processed by thefractional PLL element 265, the VCO 270 and the LPF 275. The VCO 270receives an input signal along connection 267, which is coupled to theoutput of the fractional PLL 265. The output of the VCO 270 is coupledvia connection 274 to the LPF 275. The output of the LPF 275 is coupledvia connection 276 to the fractional PLL 265. In accordance with anadjustable number N, the combination of the fractional PLL element 265,the VCO 270 and the LPF 275 generate an output signal on connection 275having a frequency that is N times the channel reference frequencyprovided on connection 252. The output signal on connection 275 is finetuned in one or more of phase, frequency or amplitude as required beforebeing forwarded along connection 285 to the 90° phase shifter.

Digital data is received by the I/Q generator 136 via connection 128.The I/Q generator 136 generates modulated I and Q data signals inaccordance with the 8PSK modulation standard. In the embodimentillustrated in FIG. 2, the I/Q generator 136 functions in cooperationwith the I/Q controller 152. As will be explained in greater detail inassociation with FIG. 3, the I/Q generator 136 selects and provides apreviously stored waveform in response to the data received onconnection 325 to the I/Q controller 152. The I/Q controller 152provides a data interrupt signal along connection 153 and a data outputsignal along connection 335.

When data is not interrupted by the I/Q controller 152, the I datasignal is forwarded from the I/Q generator 136 via connection 201 to theDAC 202 and the Q data signal is forwarded from the I/Q generator 136via connection 203 to DAC 204. The DAC 202 is coupled to LPF 206 viaconnection 205. The DAC 202 converts the I data signal into an analogsignal, which is low-pass filtered by LPF 206 before being forwarded tothe mixer 220 via connection 209. The mixer 220 receives a localoscillator signal from 90° phase shifter 210 along connection 212. Thelocal oscillator signal, when applied by the mixer 220 upconverts the Idata signal from a baseband frequency to a RF transmission frequency.The I data signal at the RF frequency is forwarded to node 240 viaconnection 224.

When data is not interrupted by the I/Q controller 152, the Q datasignal is forwarded from the I/Q generator 136 via connection 203 to theDAC 204. The DAC 204 is coupled to LPF 208 via connection 207. The DAC204 converts the Q data signal into an analog signal, which is low-passfiltered by LPF 208 before being forwarded to the mixer 230 viaconnection 211. The mixer 230 receives a local oscillator signal from90° phase shifter 210 along connection 214. The local oscillator signalon connection 212 is at a first or reference phase. The local oscillatorsignal on connection 214 is shifted 90° from the local oscillator signalon connection 212. The local oscillator signal on connection 214, whenapplied by the mixer 230, upconverts the Q data signal from the basebandfrequency to the RF transmission frequency. The Q data signal at the RFfrequency is forwarded to node 240 via connection 234. The I and Q datasignals are added by the node 240 and applied at an input to thevariable gain amplifier 250 along connection 245. The variable gainamplifier 250, in accordance with a gain control signal applied atconnection 251, amplifies the composite data signal and forwards theamplified data signal on connection 255 to the power amplifier 160.

The power amplifier 160 in accordance with the power control signal onconnection 195 further amplifies the composite data signal on connection255 and forwards the power amplified composite data signal viaconnection 161 to the front end module 162 and antenna 165.

FIG. 3 is a schematic diagram of an embodiment of the digital or 8PSKmodulator 300 of FIG. 2. The 8PSK modulator 300 includes a data receiverelement 305, a symbol rotator 310, a read-only memory element 320, theI/Q controller 152 and an accumulator 340. The data receiver element 305receives the digital data signal on connection 302. The 3-bit gray codedEDGE symbol, is forwarded to the symbol rotator 310 via connection 307.The symbol rotator shifts the received gray coded EDGE symbol by 3π/8 asdirected by the EDGE (8PSK) modulation standard. As indicated by thefour time slots labeled T0, T1, T2 and T3, the phase shifted (i.e.,rotated) gray coded EDGE symbol comprising an I and a Q componentidentify a symbol address Si. The symbol address, which is dependentupon the values of I and Q is used to direct the read-only memoryelement 320 to forward a previously stored representation of a waveformSi on connection 325 to the I/Q controller 152. The I/Q controller 152processes the received waveform on connection 325 in accordance with aramp transition signal forwarded from the baseband subsystem 110 on bus132. As shown in FIG. 3, the ramp transition signal is at a logic 0level before and after a ramp down transition. Conversely, the ramptransition signal is at a logic 1 during a ramp down transition. Theramp transition signal on connection 132 is at a logic 1 before aramp-up transition and remains at a logic 0 during normal transmissionor flat area of transmit time mask. The ramp transition signal onconnection 132 is at a logic 1 again during ramp-down transition afterthe flat area of transmit time mask. The accumulator 340 receives theoutput waveform after processing by the I/Q controller 152 viaconnection 335. The accumulator 340 processes the previously storedwaveform in accordance with a clock signal provided on connection 342and forwards an I data signal on connection 201 and a Q data signal onconnection 203. The accumulator 340 integrates and filters the timevarying data represented by the stored waveform to meet the power vs.time mask and spectrum requirement specified by the EDGE communicationstandard.

In the illustrated embodiment, the I/Q controller 330 includes a logicinverter 332 and logic AND gate 334. The logic AND gate 334 receives afirst input via connection 325 from the read-only memory element 320 anda second input on connection 333 from the output of the inverter 332.The combination of the inverter 332 and AND gate 334 generates a logic 0at the output of the I/Q controller 152 (i.e., on connection 335) whenthe input to the combination on connection 132 is at a logic 1 and thedata from the read-only memory element 320 on connection 325 is at alogic 1. Otherwise, the inverter 332 and AND gate 334 forward the dataon connection 325 from the read-only memory element 320 via connection335 to the accumulator 340. Entering a logic zero at the input to theaccumulator 340 reduces the output of accumulator 340 smoothly andprovides a ramp transition on the I and Q signal.

FIG. 4A is a graphical representation of the relationship between thepower vs. time mask as defined by the EDGE communication standard (8PSKmodulation) and the modulated data signal output power. Plot 400 depictstime (μsec.) along a horizontal axis and relative power (dBc) along thevertical axis. A reference time or 0 μsec approximately defines thecenter of the represented data transmission. Example timing signals areshown below the plot. Trace 440 represents a signal labeled TX_SW. TheTR₁₃ SW signal defines a data transmission period during which datasymbols will be transmitted from the handset. The trace 450 represents aramp transition signal. The trace 450 changes from a logic 0 level to alogic 1 level just before a ramp up transition is desired in themodulated data signal power. The trace 450 returns to logic level 0during the data transmission as indicated by the relation to the TR_SWsignal. The trace 450 changes from a logic level 0 to a logic level 1just before a ramp down transition is desired in the modulated datasignal power. The trace 450 returns to logic level 0 after the ramp downtransition and the completion of the data transmission.

Trace 410 represents the upper limit of the power vs. time mask asdefined by the EDGE standard for 8PSK modulation. Trace 420 representsthe lower limit of the power vs. time mask as defined by the EDGEstandard for 8PSK modulation. To be compliant, the modulated data signalpower should remain within the upper and lower limits before, during andafter burst transmissions. An example modulated data signal power overtime generated by the system 300 (the system including the 8PSKmodulator and the I/Q controller 152) is represented by trace 430. Asindicated in FIG. 4A, the trace 430 ramps or transitions smoothly from−40 dBc to approximately 4dBc from approximately −280 μsec. to −275μsec. The measurement unit dBc is indicative of decibels relative to acarrier frequency. Thus, dBc specifies the power of a sideband in amodulated signal relative to the carrier in decibels.

The described ramp-up transition occurs in conjunction with the ramptransition signal provided on connection 224 to the I/Q controller 152(FIG. 3). A data transmission period coincides with the peaks of thelower limit of the power vs. time mask as indicated by trace 420. Duringthe data transmission, the trace 430 varies in amplitude betweenapproximately 4 dBc to approximately −10 dBc. Thereafter, the trace 430ramps or transitions smoothly from approximately 4 dBc to below −40 dBcfrom approximately 275 μsec to 280 μsec.

FIG. 4B is a graphical representation of the relationship between thepower vs. time mask as defined by the EDGE communication standard (8PSKmodulation) and the modulated data signal output power represented bytrace 430. The time scale in FIG. 4B coincides with the period from −300μsec to −200 μsec as indicated by the dashed line in the plot of FIG.4A. As indicated in FIG. 4B, the modulated data signal output powerremains within the upper and lower limits (i.e., within the boundariesdefined by trace 410 and trace 420) of the EDGE communication standardpower vs. time mask.

FIG. 5 is a flow chart illustrating the operation of an embodiment of amethod for initiating ramp power transitions in a mobile handsettransmitter. The flow diagram of FIG. 5 shows the architecture,functionality, and operation of a possible implementation via softwareand or firmware associated with a controller arranged with a digitalmodulator in a direct launch transmitter. In this regard, a block canrepresent a module, segment, or portion of code, which comprises one ormore executable instructions for implementing the specified function(s).When a controller (associated with the digital modulator) is implementedvia hardware, hardware and firmware or a combination of hardware andsoftware, one or more blocks in the flow diagram may represent a circuitor circuits. Alternatively, the described functions can be embodied insource code including human-readable statements written in a programminglanguage or machine code that comprises instructions recognizable by asuitable execution system such as a processor in a computer system. Themachine code may be converted from the source code, etc.

Method 500 begins with block 502 where a controller is inserted betweena memory element and an accumulator of a digital modulator. Thereafter,as indicated in block 504, the controller interrupts the transfer ofstored symbols from the memory to the accumulator, by inserting a logic0 at the input to the accumulator, in response to an indication that thetransmit power should be transitioned.

FIG. 6 is a flow chart illustrating the operation of an embodiment of analternative method for initiating ramp power transitions in a mobilehandset transmitter. The flow diagram of FIG. 6 shows the architecture,functionality, and operation of a possible implementation via softwareand or firmware associated with a controller arranged with a digitalmodulator in a direct launch transmitter. In this regard, a block canrepresent a module, segment, or portion of code, which comprises one ormore executable instructions for implementing the specified function(s).When the controller (associated with the digital modulator) isimplemented via hardware, hardware and firmware or a combination ofhardware and software, one or more blocks in the flow diagram mayrepresent a circuit or circuits. Alternatively, the described functionscan be embodied in source code including human-readable statementswritten in a programming language or machine code that comprisesinstructions recognizable by a suitable execution system such as aprocessor in a computer system. The machine code may be converted fromthe source code, etc.

Method 600 begins with block 602 where a controller is inserted betweena memory element and an accumulator of a digital modulator. Thereafter,as indicated in block 604, the controller interrupts the transfer ofstored symbols from the memory to the accumulator, by inserting a logic0 at the input to the accumulator, in response to an indication that thetransmit power should be transitioned. While the controller isinterrupting the transfer of stored symbols from the memory to theaccumulator the control input of the variable gain amplifier in thedirect launch transmitter is being held constant as shown in block 606.Additionally, as indicated in block 608, a control signal applied to thepower amplifier in the direct launch transmitter is held constant. Thecombination of keeping the gain of the variable gain amplifier constantand the control signal to the power amplifier constant while applyingthe power transition signal enables the digital modulator to provide thedesired frequency and time domain responses during ramp up and ramp downtransitions of the transmit power level.

While various embodiments of the digital modulator, the I/Q controllerand method for initiating ramp power transitions in a mobile handsethave been described, it will be apparent to those of ordinary skill inthe art that many more embodiments and implementations are possible thatare within the scope of this disclosure. Accordingly, the digitalmodulator, I/Q controller and method are not to be restricted except inlight of the attached claims and their equivalents.

1. A method for initiating ramp power transitions in a mobile handsettransmitter, comprising: inserting a controller between a memory elementand an accumulator in a modulator; and controllably directing thecontroller to alter the transfer of stored symbols from the memoryelement to the accumulator by applying a logic 0 at an input of theaccumulator in response to an indication that the transmit power shouldbe transitioned while maintaining the transmit time mask requirements.2. The method of claim 1, wherein controllably directing the controllerto interrupt the transfer of stored symbols comprises sending a signalto the controller before a ramp up transition is desired.
 3. The methodof claim 2, wherein sending a signal to the controller when a ramp uptransition is desired comprises sending a signal representative of theduration for communicating N symbols from the memory to the accumulator.4. The method of claim 1, wherein controllably directing the controllerto interrupt the transfer of stored symbols comprises sending a signalto the controller when a ramp down transition is desired.
 5. The methodof claim 4, wherein sending a signal to the controller when a ramp downtransition is desired comprises sending a signal representative of theduration for communicating N symbols from the memory to the accumulator.6. The method of claim 1, wherein inserting a controller between amemory element and an accumulator comprises inserting digital logic. 7.The method of claim 6, wherein inserting digital logic comprisesinserting an inverter and an AND gate.
 8. The method of claim 7, whereininserting an AND gate comprises coupling a first input of the AND gateto the output of the memory.
 9. The method of claim 7, wherein insertingan AND gate comprises coupling a second input of the AND gate to acontrol signal.
 10. The method of claim 7, wherein coupling the secondinput of the AND gate to a control signal comprises applying a basebandgenerated signal.
 11. The method of claim 7, wherein inserting an ANDgate comprises coupling an output of the AND gate to an input of theaccumulator.
 12. The method of claim 1, further comprising: holding again of a variable gain amplifier in the transmitter constant.
 13. Themethod of claim 1, further comprising: maintaining a control input to apower amplifier in the transmitter constant.
 14. A digital modulator fora portable handset that uses a direct launch transmitter, the digitalmodulator, comprising: a memory; an accumulator; and a controllercoupled between the memory and the accumulator, the controllerconfigured to alter the transfer of stored symbols to the accumulator inresponse to an indication that a transition is desired in the transmitpower of the portable handset.
 15. The digital modulator of claim 14,wherein the controller comprises a logic gate and an inverter.
 16. Thedigital modulator of claim 15, wherein logic gate comprises an AND gate.17. The digital modulator of claim 14, wherein the controller receivesthe indication from a signal that originates in a baseband of thehandset.
 18. The digital modulator of claim 14, wherein the controllerinterrupts the communication of symbols to the accumulator.
 19. Thedigital modulator of claim 18, wherein the controller interrupts thecommunication of symbols to the accumulator for the duration of twosymbols.
 20. The digital modulator of claim 18, wherein the controllerinterrupts the communication of symbols to the accumulator before a rampup transition and at a ramp down transition.